Patients with inflammatory bowel disease (IBD) have a 20 to 30-fold increased risk of colorectal cancer relative to the general population. This increased cancer risk has been attributed to genetic damage from oxidative stress caused by inflammatory mediators combined with the proliferation of colonic epithelium during mucosal repair. IBD-associated neoplasia can be detected at an early, potentially curable stage by colonoscopic screening. However, safe and effective new strategies for preventing colon cancer would be of great benefit to IBD patients and should ultimately lead to considerable cost savings. Recent animal studies have shown that inhibiting T cell-mediated colon inflammation can decrease the risk of colon cancer. Our studies show that oral administration of bromelain, a proteinase mixture derived from pineapple, significantly decreases both the incidence of spontaneous colitis and the severity of established T cell-mediated colitis in IL-10-deficient mice. Previous in vitro studies by our laboratory and others have shown that bromelain decreases T cell proliferation, signal transduction, and cytokine production. Its anti-inflammatory effects in vitro and in vivo depend on its proteolytic activity. This proposal is designed to test the hypothesis that bromelain treatment will decrease the risk of IBD-associated colon cancer by decreasing the genetic damage caused by T cell-mediated inflammation. The specific aims will determine the effect of bromelain on inflammation and development of colon neoplasia in mice with chronic T cell-mediated colitis. The severity of inflammation and the incidence of colonic neoplasia will be determined histologically. Inflammation-associated oxidative lesions in DNA and treatment-related effects on signal transduction and critical biomarker expression will be determined to directly assess effects of bromelain on pathways critical to inflammation and colorectal carcinogenesis. The proposed studies will further elucidate mechanisms that can lead to novel interventions to prevent IBD-associated colon cancers, providing great benefit to IBD patients and their families.